I think I've got it figured out.
To run the Trailblazer with JBoss AS, you have to configure mail properties in the jbossesb-properties.xml file within jbossesb.sar.
When deploying 4.3.GA to a JBoss AS, the ESB "deploy" task copies the distributed jbossesb.sar to the JBoss AS deploy directory. As distributed, this
archive defines the smtp server as "localhost".
The documentation seems to favor stand-alone deployment of JBossESB.
Thanks for comment.
Yes, it needs to update the "jbossesb-properties.xml" in the jbossesb.sar, it seems it has not been clearly described (it should say in jbossesb.sar) the TrailblazerGuide. Will update it later...